Vulcanization

Raw RUBBER is sticky and plastic. It hardens in cold and softens in heat, and it is not elastic. In 1839, Charles Goodyear discovered that by combining raw rubber with sulfur and heating it, the rubber became stronger, elastic, unaffected by heat and cold, and resistant to solvents. Today almost all rubber, as well as synthetic rubber, is vulcanized. The degree of hardness varies directly with the amount of sulfur and heat used in the process.

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In the whole world there are only five mountains more than five miles high. They are all in the Himalayas. Mt. Everest is the highest ...

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THE ONE DOLLAR BILL

The United States one-dollar bill is the most common denomination of US currency, totaling 45% of all bills ($1, $2, $5, $10, $20, $50 and $100) produced. There are about 2 billion $1 bills in circulation.

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SUGAR IN THE MIDDLE AGES

In the Middle Ages, sugar was a treasured luxury costing 9 times as much as milk. Ironically, now that sugar is plentiful, sugar-free products are more popular than ever before.

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What is a depressant?

A depressant is a drug that reduces the activity of various body functions. Some depressants such as anesthetics, sedatives, antiepileptics, narcotics analgesics, and some muscle relaxants, slow nervous and muscular activity by acting on the central nervous system. Tranquilizers are depressants that affect only part of the nervous system. They induce relaxation without causing total depression.